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Mrs Middleton’s guide to passing This Powerpoint is part of a set uploaded to the shared area designed to give you all the information you need to pass your GCSE exam. Use the hyperlinks to take you to the sections and pages you need to cover as well as external links to other useful sites. You snooze… you loose…Read this for maximum marks
Useful Resistant Materials Properties of materials Softwoods Hardwoods Manmade/ manufactured boards Pressure treated timber Conversion of timber Seasoning Warping/ wood finishes Marking out wood/metal & plastic Cutting Drilling wood/ metal & plastic Glues and adhesives Ergonomics Anthropometrics CAM Metals/ marking out Cutting and drilling metals Taps and dies Heat treating Metals Tempering steel Files and filing Finishes for materials METALS Finishes for materials PLASTICS Finishes for materials WOOD Plastic/powder coating Metals definition of Ferrous metals and their uses Non Ferrous metals and their uses Brazing – how to Pillar drill safety Milling/ CNC machine Jigs, moulds & templates Test yourself - tools Click button to come back to the contents page, or enter to continue to next page
The Wood Lathe Click on a coloured title to go to that section The Centre Lathe Test yourself – wood Screws Test yourself – metal Nails Main parts of the lathe Rivets Examples of turned work 4 types of Wood Joints Carcase/ box frame Stool frame Slab construction Flat frame Wood turning tools Riveting facing off/ chamfering Hinges Drilling on the Lathe KD fittings Definition of Plastics Thermo & thermosetting plastics Smart materials nylon Marking out, cutting & filing Extrusion moulding Injection moulding Blow moulding Vacuum forming Compression moulding Calendaring Line bending Rotational moulding Plastic coating Word search Plastics that break down 4 types of mechanisms Cams Gears Rack and pinion Worm gears Pulley systems Cranks Ratchets Linkages Click button to come back to the contents page, or enter to continue
Useful Resistant Materials Types of What are they Examples. All pure metals Aluminium, Copper, Tin, Zinc Ferrous Alloys These are a mixture of iron and other materials such as carbon, tungsten etc Mild Steel Tool Steel Stainless steel Cast Iron Non Ferrous Alloys These metals contain no iron in them Aluminium Alloys Brass, Solder. Hardwoods In U. K. broad leaved trees are hardwoods and trees with needle like leaves are softwoods. Lots of softwoods are treated for longer useful life. Commonly known hardwoods are ash, beech, mahogany and oak These are wood made by man from both hardwoods and softwoods MDF is very often used in school products as is Plywood These plastics soften when heated. Heat can be used to change their shape Many everyday products are made from these thermoplastics. Acrylic, PVC, nylon, polystyrene, and expanded polystyrene These once they have been moulded into a shape would rather smoulder or burn or ignite when subject to high temperatures. Their characteristic of not softening when heated make them useful for saucepan handles and worktop laminates and melamine ‘Smart’ materials respond in a certain predictable ways to changes in temperature, light, or pressure: These responses can be put to good effect because they occur predictably in response to stimuli that are input to them. . Examples are shape memory alloy (SMA) such as Nitniol, polymorph, a low temperature setting plastic and modern materials in traditional applications such as the use of carbon fibre in fishing rods and keylar in safety protection helmets; plastazotes which are nitrogen blown inert foams. Elements Softwoods Manufactured Boards Thermoplastics Thermosets Scotch pine and Spruce are softwoods used in many everyday applications.
Malleability is a property of a material that describes the ease with which its shape can be changed by hammering, rolling, forging or pressing. Gold is the most malleable material followed by aluminium. Copper, lead, tin and iron are also very malleable. Heating a material causes an increase in its malleability. Impurities however can cause a degradation in the malleability of some materials. Ductility Elasticity Hardness Brittleness Toughness Conductivity this is an ability of a material of being plastically stretched (flow) without breaking or fracturing. Steel and copper are highly ductile. The ductility of a material is measured by a tensile test on a testing machine. Samples of the material are held at both ends and a stretching force is applied until the sample breaks. is the ability of a material to regain its shape after being deformed. A rubber band is very elastic as it regains its shape when tension is removed. is the ability of a material to resist being scratched or cut. extremely hard and therefore breaks easily. ex glass. is a measure of a material's ability to absorb energy before fracture. ability to conduct heat, electricity sound radiation etc. The material acts as a medium of transport.
SOFTWOODS Scots Pine Description: Large evergreen and only native British Pine. Where found: Found from Spain to Siberia. Uses past & present: Strong general purpose timber. Cedar They are grown for their durable (decay-resistant) scented wood The wood is also used for humbler purposes requiring resistance to weather, such as shakes and shingles. Cedar wood and cedar oil is known to be a natural repellent to moths, hence hope chests were made of cedar when available. Cedar is a popular lining for modern-day closets in which woollens are stored. Cedar (Cedrus) is a genus of coniferous trees in the plant family Pinaceae. They are most closely related to the Firs, sharing a very similar cone structure. They are native to the mountains of the western Himalaya and the Mediterranean region, Uses of wood - Preservatives are effective on this wood hence suitable for outdoors. Used for fencing, joinery, building, flooring, box and packing case manufacture, railway sleepers, pitwood, fibreboard, chipboard, and telegraph poles. Referred to by the timber trade as "redwood" or "deal". Food and drink The needles yield a medicinal oil also pitch, tars, resin and turpentine obtained from the wood.
Hardwoods Description: Magnificent, large, deciduous tree. Important economic forestry tree. Ash is a straight moderately open grained hardwood with a Beech Height: Max 40 m. Age: mature at 120 years The European species, yields a utility timber that is tough but dimensionally unstable. texture ranging from medium to coarse (due to porous wood spring growth). The colour of Ash can vary from a pale creamy to brown. Alight coloured wood, cream to light brown, with a bold, straight grain. externally non durable but suitable for all internal woodwork It is tough and has good steam bending qualities. It is good turnery wood. It takes stains and finishes to a dull shiny surface. It lends itself Beech wood is an excellent firewood, easily split and burning for many hours with easily to machining processes. bright but calm flames. Chips of beech wood are used in the brewing of Budweiser beer as a fining agent. Beech logs are burned to dry the malts used in Ash is used internally in many applications such as some German smoked beers, to give the beers their typical flavor. furniture, cabinets, joinery, mouldings, panelling, kitchen Beech wood is excellent for furnitures as well. worktops, staircases, shop fittings. It is also very good for tool handles, hockey and hurley sticks as well as boat building. is a large, fast-growing tree that can grow up to 30 m (100 ft) tall, native to tropical It is widely used for furniture framing and carcass construction, flooring and engineering purposes, in plywood and in household items like plates, but rarely as a decorative timber. Balsa The timber is very soft and light with a coarse open grain. The density of dry balsa wood ranges from 100– 200 kg/m³ (6. 24 -12. 49 lb/ft³), with a typical density of about 140 kg/m³ (8. 74 lb/ft³) (about one third the density of other kinds of hard wood). This makes it a very popular material for model building and buoyancy materials (lifebelts, etc. ), and was famously used by Thor Heyerdahl in his raft Kon-Tiki. It is also a very popular material to use when making wooden crankbaits for fishing, as it is low density but high in strength. Balsa wood is used to make very light, stiff structures in model bridge tests and for the construction of light wooden aeroplanes, most famously the World War II de Havilland Mosquito. In table tennis blades, a balsa layer is typically sandwiched between two pieces of thin plywood. Balsa wood is also used for making high-quality balsa surfboards. Balsa South America north to southern Mexico. It is evergreen, or dry-season deciduous if the dry season is long, with large (30– 50 cm, 12 -20 in) weakly palmately lobed leaves. The name balsa derives from Spanish for a raft. Despite being very soft, balsa is classified as a hardwood, the softest commercial hardwood.
Common Oak Description: Large deciduous tree and probably our commonest tree. Height 30 - 40 m. Age 1000 year or more. Oak The oak is a common symbol of strength and endurance and has been chosen as the national tree of for such countries as England, France, Germany, USA. Uses Oak wood is very resistant to insect and fungal attack because of its high tannin content. It also has very attractive grain markings, particularly when quarter-sawn. Wide, quarter-sawn boards of oak have been prized since the Middle Ages for use in interior panelling of prestigious buildings such as the debating chamber of the ritish House of Commons in London, B England, and in the construction of fine furniture. Oak wood, was used in Europe for the construction of ships until the 19 th century, and was the principal timber used in the construction of European timber-framed buildings. Today oakwood is still commonly used for furniture making and flooring, timber frame buildings, and for veneer production. Barrels in which red wines, sherry, brandy and spirits such as Scotch whisky and Bourbon whiskey are aged are made from European and American oak. The name mahogany is used when referring to numerous varieties of dark-coloured wood, known as West Indian or Cuban Mahogany is the national tree of Dominican Republic. Mahogany has a generally straight grain and is usually free of voids and pockets. It has a reddish-brown colour which darkens over time, and displays a beautiful reddish sheen when polished. It has excellent workability, and is very durable and slow to rot. These properties make it a favourable wood for boat making, as tradition has shown, as well as for making furniture and upholstery, musical instruments, and other durable objects. Some of the gift shops in the Caribbean especially St. Croix offer Cuban Mahogany in the form of jewellery. Mahogany is a very popular material for drum making, because of its great integrity and capability to produce a very dark, warm tone The famous Beatles sound of the 60 s was made with Ludwig Drums in mahogany shells. A wide variety of electric guitars are also made from mahogany. Mahogany is a very popular choice of material for Luthiers constructing all grades of acoustic guitars. Often mahogany is used for the back and sides of the guitar, while cedar and spruce, or another lighter-coloured and more loosely-grained wood is used for the top. Mahogany
Manmade Board MDF – Medium Density Fibreboard PROPERTIES MDF is an ecologically friendly engineered wood product that is dense, knot free and available in large sizes and thicknesses. It is easy to work with using workshop tools and equipment. It has no grain and can be drilled, filed sawn etc. MDF may be finished using methods such as painting, varnishing, veneering and laminating. USES It is for internal use only and is used to make lots of modern furniture such as kitchen units, cupboards, shelves, wardrobes etc. In these applications the mdf is laminated to give the impression that it is made from natural timber. It is also used as a substitute for floorboards, cornices, skirting boards and architraves. Mdf is made from wood fibres that are compressed and glued using formaldehyde resins. It is produced at different densities typically ranging from 160 to around 800 kg/m³. MDF can be made out of trees that would otherwise have been cut and burnt causing pollution. Wood Chips can also be used to manufacture Mdf. Health&Safety MDF contains urea formaldehyde which can cause irritation to the eyes and lungs. This may be released from the material during cutting and sanding using machinery. Proper ventilation is required when using it and facemasks are needed when sanding or cutting MDF with machinery. Masks and goggles should always be worn at all times.
PLYWOOD is an ecologically friendly engineered product whose finish quality varies considerably, some plywood have attractive grains while others can contain knots. Plywood is graded for exterior or interior use depending upon the water resistance of the glue used to stick the plies together. USES Interior grade plywood does not contain water-resistant adhesive. It may be used for wall panelling, flooring and furniture. Exterior grade plywood (WBP - Weather and Boil Proof) can be used outside. Water-resistant adhesives are used and can resist a certain amount of moisture. Sheds and cladding are made from this material. All Weather boiled proof plywood requires paint or varnish to protect the outer veneer from the elements. Shuttering boxes are made from shuttering plywood. Shuttering boxes are used in the construction industry to contain concrete while it sets. The material is water resistant to a certain extent. The surface of this material does not have a decorative veneer and is generally not suitable for use where an attractive quality finish is required. Marine Plywood is made with waterproof adhesive so that it can be used under water. Plywood can be nailed and screwed. Thin plywood is flexible and can be formed into curved shapes. Plywood is made by gluing layers of wood veneer at right angle to one another. This results in the direction of grain in adjacent layers to be perpendicular to each other. Plywood is manufactured in odd number of layers such a 3 ply, 5 ply, 7 ply etc. The crossing over of the grain in each layer adds stiffness, strength and stability to the product. Suitability for outdoor use depends on the glue used in the manufacture of this product. Marine ply is often used in boat Plywood is sold in 2440 x 1220 mm and 1525 x 1525 mm sheets. Common thicknesses are 3, 4, 6, 9, 12, 22 and 25 mm.
BLOCKBOARD - This is built up with a core of softwood strips bonded together with adhesive and covered with a sheet of plywood on either side. Used as a building material and for furniture manufacture including fitted kitchens / bedrooms. HARDBOARD - This is made from wood fibres that have been pulped. The pulp is put under pressure until the fibres bond to produce a tough board that is smooth on one side and rough on the other. It is not as strong as the other boards. Often used for back of furniture. CHIPBOARD - This is made up of small chips of wood bonded together with resin and formed into sheets by compression. It is not as strong as plywood and block board but it is not expensive. Chipboard is often covered with a plastic laminate or wood veneer and used in furniture. Manufactured boards available in sheet sizes 2440 X 1220 generally available in thickness 3, 6, 9, 12, 18, 22, 25 mm and occasionally greater.
PRESSURE TREATED TIMBER Advantages of Pressure Treated Timber This is timber which has been impregnated with wood preservative under controlled conditions. Suitable timbers for treatment are all softwoods, commonly used hardwoods and exterior grade plywoods. Pressure treated timber has a long service life and is protected against fungal and insect attack. Environmental impacts that arise from the use of treated wood? Extends the useful service life of the timber commodity and helps optimise the use of one of man’s few renewable resources It allows wood to be used in many end use situations because it is protected from biological agencies. Otherwise, alternative materials such as concrete, steel, plastic and aluminium would be used. When considered on a life cycle basis these materials have higher negative environmental impacts than treated wood. It can be disposed of either by land-fill or burned in an approved industrial or commercial incinerator or boiler, when the embodied energy in the timber can be realised. Beech is whitish to light pink in colour. While it is a good turnery wood, it is also suitable for furniture, cabinet making and various aspects of joinery. Close grained. Tends not to splinter. Ideal for children’s toys. Ash A light coloured wood, cream to light brown, with a bold, straight grain. It is suitable for high-class cabinet making, interior joinery as well as most aspects of furniture making, possessing a good resistance to splitting and takes stain well. Reasonably flexible. ( hockey sticks, handles for hammers, axes) Mahogany Ranging from a yellowish through to reddish, pinkish and up to a deep brown with age, It is highly suitable for all aspects of furniture from chairs to wardrobes, as well as interior construction. SOFTWOODS Western Red Cedar It is ideal for rustic furniture, cabinet-making, and garden decking. It has an in built chemical that preserves it from insect attack. Often used outdoors. Remarkably knot free, strong. Douglas Fir is often considered to be one of the best known softwoods. Reddish brown colour. Used in window fames, ladders and indoor furniture. Spruce (Whitewood). A softwood with a creamy yellow colour. Used both indoors and outdoors ; scaffolds, wooden containers and wardrobes
CONVERSION OF TIMBER Conversion means sawing logs into usable sizes with minimum waste. The 2 main methods are PLAIN SAWING and QUARTER/ RADIAL SAWING. PLAIN SAWN - Plain sawn, or Flat sawn, is the standard way of cutting logs into lumber, or flooring. Plain sawn can produce wide grain patterns (depending on the wood species) QUARTERSAWN - Quarter sawing, means that the log is cut at right angles to the growth rings. This flooring has a very decorative grain patterns and produces more stability during changes in humidity. Quartersawing is more difficult, more expensive and slower to produce and wastes more wood Quartersawn wood twists and cups less and wears more evenly than other cuts. Quartersawn boards usually show a heavy fleck pattern. Quartered sawn timber is more stable because the expansion and contraction across the face of the board when exposed to temperature and humidity fluctuations, is much less than in plain sawn lumber.
Seasoning is the removal of excess moisture from wood by drying it after it has been converted. Green timber has around 85% moisture content. It is the aim to reduce moisture content to less than 18% for Timber for general use and 12% for centrally heated and air conditioned buildings. The 2 ways to season timber are: AIR SEASONING – the natural method Boards are stacked in the open air with thin strips of wood between them so that the air can circulate. The stack is raised clear of the floor and has a roof to protect it from the weather. The end of the planks are painted to prevent the end grain from drying too quickly and causing splitting. KILN SEASONING – the artificial method Boards are stacked on a trolley with srips between them and put in a kiln. 1 Steam is injected at low temperature to force free moisture out of the wood cells 2 Steam is reduced and temperature is increased to dry wood 3 Finally there is a flow of hot air ADVANTAGES It is cheap and needs little skill attention. Disadvantage Takes 3 -6 years to dry. Moisture content can only be reduced to 1518 % Advantages It only takes a few days or weeks to dry and it kills any insect eggs e. g woodworm in the wood. It is possible to reduce the moisture content to 12% for use in centrally heated builings Disadvantages Kilns are expensive to build and run as incorrect drying temp’ and times will ruin the wood.
When ordering wood you give the rough sawn measurement, if you are ordering planed wood this will then arrive approx 3 mm smaller. (PAR = planed all round & PBS = planed both sides) Boards Common thicknesses are 12, 16, 19, 22 and 25 mm A plank is a piece of wood over 40 mm thick Common widths between 75 mm and 330 mm depending on the wood. Lengths are normally between 1. 8 metres and go up to 6. 3 metres Warping Square sections Common sizes for squares are 25 mm x 25 mm, 38 mm x 38 mm and 50 mm x 50 mm is a general term given to any distortion in the shape of the woods true shape, there are 4 ways this can happen: Cupping – a curve across the grain Bowing – a curve along the grain Springing – a curve along the edge Twisting or winding – curving like a propeller Wood Finishes are used to protect the surface of the wood from the weather, insect attack, fungal attack, heat, liquids and dirt, and to improve the appearance of the wood. Click here to see more information on wood
Marking Out in Wood Metal or Plastic. (These are the equipment that we have used in our projects. ) Marking Out Checking flatness Marking square Drawing parallel lines Drawing angles Drawing circles Marking indent (for drilling or setting up compass) Material Measuring Wood Steel rule Pencil/ marking knife Steel rule Tri –square Marking gauge Sliding bevel Dividers/ compass Centre punch or bradawl Metal Steel rule Scribe Steel rule Engineers square Odd leg calipers Sliding bevel Dividers/ compass Centre punch plastic Steel rule OHP pen Steel rule China graph pencil Tri - square Odd leg calipers Sliding bevel Dividers/ compass Centre Masking tape
Cutting Out and shaping Wood Metal or Plastic. (These are the hand tools that we have used in our projects) Remember that just saying "saw" in the exam will get you no marks. So be specific in your answers. Tenon saw Coping saw Hacksaw Junior hacksaw hand? / panel saw files rasps Tin snips (cutting straight Lines) (curvy lines) Wood yes no no yes yes no Metal solid section no no yes no no Sheet metal no no yes Plastic yes yes no no Material
Glues and Adhesives WBP ~ Weather and Boil Proof BR ~ Boil Resistance MR ~ Moisture Resistance INT ~ Internal only For restoration work, veneering and other applications where compatibility with original artefacts is needed. scotch glue Used extensively in the musical instrument industries. It is for internal use only and has high gap filling properties. Fish glue General joinery and woodwork use Casein. It may stain some hardwoods and oak is particularly prone to darken. Developed in WW 2 for the manufacture of the Mosquito plane which was largely made of fabricated plywood panels. Where great strength is required, durable and water resistant. for heavy structural work and quality plywood. Phenol formaldehyde (PH) Outstanding durability qualities under the severest weather conditions and mainly for external construction work. Resorcinol formaldehyde (RF) Decorative work is not possible because it has a dark glue line. Laminating, fabricating and veneering when large presses or good cramping facilities are available. Hard decorative plastic laminates Urea formaldehyde (UF) Melamine formaldehyde (MF) Good general purpose woodwork adhesive for indoor use only. Polyvinyl acetate (PVA). Where a strong initial tack with Aliphatic resin glues (Yellow Glue) Possible has an
Glues and Adhesives - cont’d For multi-purpose applications especially for metal, plastic, ceramics and other porous or non-porous materials Polyurethane Although it foams up it does not expand or contract in the glue line. For bonding plastic laminates, sheet flooring and other fabrics, etc. to wood or other materials. Contact. ( natural and synthetic rubber) For 'tacking' jobs such as upholstery, and packaging etc. specially smaller components. Hot Melts - ethylene vinyl acetate (EVA) For bonding on many different types of materials. Epoxy Resins Joining of wood, metals, plastics and elastomers. The variety of materials requiring adhesion in the world of model making, prototyping, development and manufacturing Cyanoacrylate Adhesives
This is the symbol for people who are involved in ergonomics. Ergonomics, the Human Factor - There would not be much of a problem if you were designing and making something for yourself because you would make it fit with the way you would want to use it. However if you were designing a product for a particular market, the item designed for your own personal use may not be so suitable. Depending on the item designed, it could be uncomfortable for others to use it because there may be differences of Anthropometry size and shape ranges of people Physiology range of limb movement, strength, vision, hearing Psychology cognitive, reaction time, memory This is where ERGONOMICS comes in. Ergonomics is about using data about peoples abilities and limitations to design workspaces and tools that help people do their jobs and use their tools and other products comfortably and safely. When ergonomics is applied correctly discomfort and fatigue are reduced significantly. People are more comfortable, they can do things more quickly and easily, and they make fewer mistakes. Ergonomics is often called 'Human Factors' because it is not only concerned about the physical data but is also concerned about psychological and other aspects too. In short it is concerned about the whole person. Ergonomic design is a way of considering design options to ensure that people's capabilities and limitations are taken into account. This helps to ensure that the product is fit for use by the target users.
Anthropometric data is also required (size and shape ranges of people). With data such as this available, products can be designed so that they fit the person they are designed for. Anthropometry: This is a science that studies the dimensions of all our body parts so that products, furniture, and workstations can be designed to fit different sizes of people. It measures all our dimensions and makes recommendations about how to best apply that information. For example, it would be used to determine the best height for a child's backpack so it can fit the child's back length. Anthropometric Data Standing Person Note: The table relates to British person. The 5% percentile indicates that 5% of people are smaller than the sizes given. The 95% percentile indicates that 95% of people are smaller than the sizes given. Therefore the size range show the mid 90% range of people sizes in the UK. A head measurer from the 1900’s!
METALS How are metals made? Metals are made by mining ore from within the earth. Metal is then extracted out of the rocks in an extremely large scale industrial process. There are three main types of metals ferrous metals, non ferrous metals and alloys Ferrous These are metals which contain iron. They may have small amounts of other metals or other elements added, to give the required properties. All ferrous metals are magnetic and give little resistance to corrosion. Non-Ferrous Metals These are metals which do not contain any iron. They are not magnetic and are usually more resistant to corrosion than ferrous metals. Examples are aluminium, copper, lead. zinc and tin. Alloys: Metals are easily combined. Mixture of many metallic elements are called alloys. Examples of alloys are steel and bronze Pure Metals A pure metal only consists of a single element. This means that it only has one type of atom in it. The common pure metals are: -aluminium, copper, iron, lead, zinc, tin, silver and gold
Composition, properties and uses of ferrous metals Metal type Metal uses Mild steel - A ductile and malleable metal. Used as Nuts and bolts, Building girders, car, Mild steel will rust quickly it is in frequent bodies, gates, etc. contact with water. Properties – iron mixed with 0. 15 -0. 29% carbon. Melting point 1600°C Cast iron - Is a very strong when it is in Used as car Brake discs, car cylinders, metalwork 1200°C compression and is also very brittle. vices, manhole covers, machinery bases eg: The Properties – It is re-melted pig iron with pillar drill. small quantities of other metals. It consists of 93% iron and 4% carbon plus other elements. High carbon steel / Tool steel - Is a very Used for hand tools such as screwdrivers, 1800°C strong and very hard, resistant to abrasion. hammers, chisels, saws, spring and garden tools. It is also known as ‘high carbon’ steel or ‘medium’ steel. Properties – Up to 1. 5% carbon content. Stainless steel - is very resistant to ware Used for kitchen sinks, cutlery, teapots, cookware 1400°C and water corrosion and rust. Properties – and surgical instruments. It is an alloy of iron with a typical 18% chromium 8% nickel and 8% magnesium content. High speed steel - is a metal containing Used for drill bits, lathe tools, milling cutters on 1400°C a high content of tungsten, chromium and milling machines. It is used where high speeds and vanadium. However it is very brittle but is high temperatures are created. also very resistant to wear. Example product
Non-ferrous metals do not contain iron. Some common non-ferrous metals are aluminium, Duralumin, copper, zinc, brass, gilding metal and tin. Composition, properties and uses of non-ferrous metals: Melting point Aluminium - tends to be light in colour although it can be polished to a Used for saucepans. cooking foil, window 660°C mirror like appearance. It is very light in weight. frames, ladders, expensive bicycles. Metal type Metal uses Copper – is a ductile and malleable metal. It is often red / brown in colour. It is a very good conductor of heat and electricity. Used for plumbing, electric components, cookware and roof coverings. 1084°C Tin – Is very ductile and very malleable. It is resistant to corrosion from Used as a coating on food cans, beer cans. 231°C moisture. It is bright silver in appearance. Tinplate is steel with a tin Used as whistles, tin foil and soldering. coating. Zinc – is very resistant to corrosion from moisture. However zinc is a very weak material. Used as a coating on screws, steel buckets, 419°C American cents. It is also used to galvanise steel. Brass – Is often cast and machined then plated. It is yellow in colour and is a mixture of 65% copper and 35% zinc. It is used for decorative metal work such as 900– 940 °C door handles, candle sticks, musical depending on instruments, ornaments. composition Casting alloy – This looks like aluminium and is used for casting. It is Used for sand casting, die casting, engine 660°C aluminium with 3% copper and 5% silicon. parts, casting in schools. Example product
METALS Marking out When marking out sizes and shapes on metals it is important that we can clearly see the lines and marks. We quite often use tools that are particular to metal and not used for plastics or wood. To see marks clearly we should cover the metal in marking blue though in school we often use black marker pen before we start work. It is important to establish that the edges of your work are straight and true these edges are called datum edges and should be checked using a metal rule and engineers square When marking lines on metal we call this scribing a line we use a scribe. To mark out points, circles and parallels we use a centre punch which leaves a small indentation that can act as a centre for the drill or a pair of dividers. To mark out circles or arcs we use dividers (A compass with 2 points) To mark a parallel line to the edge of your work we use odd-leg calipers. One leg sits against the side of your work and the other scribes a line.
CUTTING AND DRILLING METALS This page shows the cutting and drilling tools used for metals. They are not always the same as the ones we use for wood or plastic. The HACKSAW is used for cutting straight lines. Ensure the teeth face forward and the blade is tight. TIN SNIPS curved or straight, for cutting shapes from sheet metal. They can be used for cutting straight lines, and round curves. Nibble the metal with short cuts rather than large ones. If you want to cut intricate shapes then a PIERCING SAW is the tool to use. Use a bench pin to support your work and cut with steady even strokes. The GUILOTINE is used for cutting straight lines in sheet material. Potentially very dangerous, make sure that the guards are in place. Hold the metal in a hand vice or with MOLE GRIPS, if necessary clamp the vice to the bed of the drill. A METAL WORKING VICE Protect delicate work from scratches by using SOFT JAWS made from wood or other soft material. The PILLAR DRILL allows you to easily and accurately drill holes with minimum effort.
Taps and Dies are tools commonly used in metalworking for the cutting of threads in metal parts Tap Wrench The Tap is used to cut a female thread on the inside surface of a predrilled hole. The three taps in the above image are of different sizes and types. The top tap has the thread going all the way to the end of the tap and is called a bottoming tap - it will tap to the bottom of the hole. To use: A hole is made (usually drilled) that is the minor diameter for that sized tap. This is the equivalent of the blank size (major diameter), less thread depth. The order of usage when hand tapping is to use the taper tap first, the intermediate next (if the material is hard and it is felt that the tap is still working too hard), and finally the bottoming tap is used to get the full form of the thread for the full depth of the shank or hole. The middle tap is an intermediate tap where thread tapers off before the bottom The lower tap is a taper tap where thread has an even more pronounced taper towards the end of the tap. This taper allows the tap to ease into the freshly drilled hole in a gradual cutting action, relieving the cutting pressure on the first few teeth of the tap. Wrench (tap holder) Taper Second Bottoming tap Tapping Drill Taper Tap Second Tap Bottom Tap
Each tool is used independently, but are usually sold in paired sets of both types, one die and three taps. Some sets however may provide a lesser number of taps. Dies Other uses An ordinary Tap or Die can also be used for repairing threads in stripped holes or bolts. Die Nuts are dies made for cleaning up old threads, they have no split for resizing and are made from hexagonal bar so that a wrench or shifter spanner can be used to apply them (rather than the purpose built die wrench) A tap wrench is a hand tool used to operate any small tool that has a square driving head as part of its body. These are usually cutting tools of which the most common are taps, however there are other small hand tools such as hand reamers that they may be employed with. The Die cuts a male thread on a preformed cylindrical rod. (on the outside) An External Screw Thread Grub screw Before cutting an external thread you must file of turn a chamfer Die inside holder Die Holder Back and forth rod Cutting teeth Chamfer rod size Die
What is Annealing Process The purpose of annealing is to soften metal and remove all strains due to rolling or hammering in the manufacturing process. Annealed metal can then be bent or machined much more easily because it is now softer. In school we often anneal aluminium before we bend it so that it does not fracture. A common method of annealing is to pack the metal in a cast-iron box containing some material, such as powdered charcoal, charred bone, charred leather, slaked lime, sand, fireclay, etc. The box and its contents are then heated in a furnace to the proper temperature, for a length of time depending upon the size of the metal. After heating, the box and its contents should be allowed to cool at a rate slow enough to prevent any hardening. It is essential, when annealing, to exclude the air as completely as possible while the metal is hot, to prevent the outside of the metal from becoming oxidized. The temperature required for annealing should be slightly above the critical point, which varies for different metals. Low-carbon steel should be annealed at about 1650 degrees F. , and high-carbon steel at between 1400 degrees and 1500 degrees F. This temperature should be maintained just long enough to heat the entire piece evenly throughout. Care should be taken not to heat the metal much above the hardening point. If only a small piece of steel or a single tool is to be annealed, this can be done by building up a firebrick box in an ordinary blacksmith's fire, placing the tool in it, covering over the top, then heating the whole, covering with coke and leaving it to cool over night. Another quick method is to heat the metal to a red heat, bury it in dry sand, sawdust, lime or hot ashes, and allow it to cool. Small sections of Aluminium can be annealed in the workshop by heating them in a brazing hearth. A good indicator that the annealing temperature is reached is to rub its surface with soap. When the correct temperature is reached the soap on the surface of the aluminium turns black. The aluminium then should then be allowed to cool slowly. When metal is heated above its critical temperature, the grain assumes a definite size for that particular temperature, the coarseness increasing with an increase in temperature. Moreover, if metal that has been heated above the critical point is cooled slowly, the coarseness of the grain corresponds to the coarseness at the maximum temperature; hence, the grain of annealed metal is coarser, the higher the temperature to which it is heated above the critical point
Tempering Steel What is Tempering Hardened steel can be tempered or made softer and less brittle by re-heating it to a certain temperature (depending on the nature of the steel and its intended use), and then cooling. When steel is tempered by the colour method, the temper is gauged by the colours formed on the surface as the heat increases. First the surface is cleaned to brightness with emery cloth so that the oxide colours will be visible to reveal the colour changes when the steel is heated. Heating can take place either by placing it upon a piece of red-hot metal, a gasheated plate or in any other available way. In school a gas torch is often used to heat the metal. As the temper increases, various colours appear on the brightened surface. First there is a faint yellow which blends into straw, then light brown, dark brown, purple, blue and dark blue, with various intermediate shades. The temperatures corresponding to the different colours and shades are given in the table on temperatures and colours for tempering. The parts are then removed from the bath and quenched in hot water. Turning and planing tools, chisels, etc. , are commonly tempered by first heating the cutting end to a cherry-red, and then quenching the part to be hardened. When the tool is removed from the bath, the heat remaining in the unquenched part raises the temperature of the cooled cutting end until the desired colour (which will show on a brightened surface) is obtained, after which the entire tool is quenched. The foregoing methods are convenient, especially when only a few tools are to be treated, but the colour method of gauging temperatures is not dependable, as the colour is affected, to some extent, by the composition of the metal. The modern method of tempering, especially in quantity, is to heat the hardened parts to the required temperature in a bath of molten lead, heated oil, or other liquids; The bath method makes it possible to heat the work uniformly, and to a given temperature with close limits.
What is CAM stands for Computer Assisted Manufacture. CAM machines normally work in conjunction with CAD programs. The CAD designs are converted into a series of instructions that dictate movement of the cutting tool in the X, Y and Z direction. This set of instructions is often referred to as G Codes. CNC machines are also computer controlled but there is human intervention programmed into the machine to make it more efficient. (rather than just the CAD design converted to Code) Advantages Of CAM Because the manufacturing process is automated and can carry out a range of operations it means that less people will be employed and items will be produced faster. Prototypes can be manufactured quickly for testing before main production. New products can be brought out quickly with a time saving of almost 35% over conventional methods. Computer controlled machines are versatile and different products can be made on them by merely changing the operating instructions. Computer controlled machines do not suffer from human errors if programmed correctly for the job. This results in fewer faulty items and lower production costs. Computer controlled machines can be programmed to take into account the properties of the material being worked on by varying spindle speed and direction, coolant, tool changing, and many other functions. This gives great flexibility to the machine and intricate components can be produced to a high specification. Efficient use of the machines leads to less breakages of cutting tools leading to lower production costs. The internet gives access to the most up-to-date design and product information quickly and easily allowing collaberation between all parties involved. Disadvantages of CAM Higher initial set up costs in purchasing computers, Computer controlled machines, programs and training operators are high. Obviously to make lots of products will require lots of machines. This can be a major drawback if the machines are not used to their optimum Computer controlled might be an advantage to the manufacturer and consumer but it leads to higher unemployment in the general labour market. Computer controlled machine require constant supervision and maintenance to ensure peak performance. Their programs can be sabotaged and need surveillance
Finishes for Materials A finish is in simple terms a coating, layer or skin applied to the material. The finish will be applied for one or more of the following reasons: . 1) To protect the material from moisture, wear, abrasion, fungus, mould or insect attack. 2) To change the materials appearance, its colour or texture. 3) To enhance the materials durability, surface hardness or other properties. Metals Type of Finish Description Polishing creates a shiny surface through the action of rubbing or the application of chemicals. These remove the oxides on the surface of the metal. The process of polishing needs repeating regularly to maintain shine. Examples Bronze and brass artefacts, aluminium, Jewellery. Lacquer can be applied to protect polished surface Wet & dry paper of the correct grit or a buffing wheels with compound of the correct grade work on the principle of rubbing over the surface of the metal. Abrasives may also be applied in paste form or as a liquid which evaporates quickly leaving a residue of powder which can be removed with a suitable cloth. The correct chemical must be used or the workpiece will be damaged. Some polishes react with zinc, a major component of brass and also a protective surface on steel. Plastic coating The metal is heated to about 150 C and dipped into a box of fluidised powdered Its very efficient in coating the handles of everyday plastic which melts onto the surface of the metal sealing it. The correct temperature artefacts. of the metal can be gauged by the colour of the heated metal. In school the metal is generally heated using a brazing hearth. Powder The most common way of applying the powder coating is to spray the powder using an electrostatic gun. The gun imparts an electric charge on the powder, which is then sprayed to the object which is grounded. The powder sticks to the object. The object is then heated in an oven at the required temperature and the powder melts to form a coating which is allowed to cure leaving a hard plastic coating on the object. coating The powder may be a thermoplastic or a thermoset polymer. It is normally used to create a hard finish on metals. Powder coating is mainly used for coating of metals, such as "white goods", aluminium extrusions and automobiles, although some other materials (like MDF-medium-density fibreboard) also can be coated in this way. http: //en. wikipedia. org/wiki/Powder_coating
Finishes for Metals cont’d Enamel (or vitreous enamel, or porcelain enamel) is the Jewellery, baths, pots and pans, colorful result of fusion of powdered glass to a substrate through oven liners the process of firing, . The powder melts and flows to harden as a smooth, durable vitreous coating on metal, glass or ceramic. It is often applied in a paste form and may be transparent or opaque when fired. Vitreous enamel can be applied to most metals. A powdered glass is melted and fused onto the metal. This requires high temperatures. This finish is very heat resistant. Painting a metal surface depends on the type of metal it is and Ferrous and non ferrous surfaces the state of the surface. such as Aluminium, brass and For ferrous metals it is desirable to first degrease the surface chrome items. with white spirit. Then the surface needs to be cleaned either with a wire brush or emery cloth followed by a metal primer (this allows good adhesion of paint to the surface of the primed metal) followed by a few coats of the desired metal paint. If it is a rusty surface, first all traces of rust should be removed followed by the application of anti-rust treatment. When dry the surface can be primed and painted. Certain manufacturers produce paint that can be applied directly to a rusty surface. Promotes adhesion for metal finish paints on non-rusting metal surfaces such as aluminium, galvanized and stainless steel, chrome, brass and copper. Special Metals Primer Oil blacking To oil black small parts, heat it till the ferrous metal surface Gun barrels are oil blacked as are changes to a dull blue grey colour (not orange or red hot!). Dip it many pieces of industrial in oil and remove immediately. "Dry" oil off with a flame. Repeat components. if necessary. Dipping the hot metal into oil leaves the metal with a thin blue/black surface layer that protect it from rust
Finishes for Metals cont’d Galvanising Chrome plating A chemical process that is used to coat steel or iron with zinc. This is done to reduce rusting of the ferrous item. Zinc coatings prevent oxidation of the protected metal by forming a barrier. Car bodies are galvanised via electroplating followed by painting with rust inhibitors. Nuts, bolts, screws hinges are routinely galvanised giving them an attractive finish Chrome plating is a finishing treatment utilizing the electrolytic deposition of chromium. The most common form of chrome plating is the thin, decorative bright chrome. It imparts a mirror-like finish to items such as metal furniture frames and automotive trim. Precision Shafts, castings, chrome plated car exhausts, bicycle wheels, Chrome plated Toilet and washbasin fittings etc
Finishes for plastics Most plastics do not require a finish as they are not susceptible to corrosion or deterioration. Plastics tend to acquire the surface finish of the mould used to form them and are rarely finished after. Type of finish Description Smoothing a plastic edge Use a smooth file along the edge of the plastic to get rid of scratches and other marks. Hold the file at an angle and let it slide over work lightly until the edge of the plastic looks smooth. Then use 220 grit sand paper followed by 400+ grit wet & dry paper with the aid of a sanding block. http: //www. sdplastics. com/acrylic. ht mlhttp: //www. delviesplastics. com/buffing% 20 compounds. htm. Acrylic polish applied on cut edges. Polishing acrylic Use a buffing wheel and the correct buffing compound. Compounds have an abrasive grit in an oil base. Buffing compounds are a solid bar that you apply to the wheel while the wheel is turning on the buffer. Hold the compound to the wheel for a few seconds, do not over apply compound to the wheel, you will only waste the compound. Run the rough edge of the acrylic against the turning wheel moving the sheet back and forth so as not to “burn” the acrylic. Buffing acrylic sheet is easy and produces crystal clear edges. Examples Acrylic polish applied on cut edges.
Wood Type of finish Description Paint http: //www. diydata. com/techniques/paintsurfaces. htm Use glasspaper to get a smooth finish over the entire surface. Apply knotting solution to any knots (follow manufacturers' instructions). Fill any voids with a suitable filler and smooth using glasspaper. Brush off all dust. Apply a coat of wood or universal primer. Internal timber - Apply undercoat and at least 1 top coat. Examples All types of wooden constructions, both internal and external. External timbers - apply undercoat and at least 2 top coats. Oil finishes These use natural and blended oils to seal and enhance the wood. They offer some moisture resistance and surface protection, some will accept a high shine others a matt or satin look. http: //www. tep. org. uk/a 2 z_glossary/a 2 z/finishes. htm Water/spirit based dyes Dyes by themselves provide little protection to the wood. To afford Furniture protection the wood can be wax polished, French Polished, or varnished. Application http: //www. blackfriar. co. uk/default. asp The wood to be dyed must be new, clean, dry and free from grease. Ensure the surface is smooth by lightly sanding along the grain with fine abrasive paper. First test Dye on an off-cut or inconspicuous area to check the colour is that required. Dye can be applied by brush but is best applied using a lint-free cloth rubbing the dye in the direction of the grain. Avoid streaks in the finish by taking care not to overlap the dye. Wipe the surface with a cloth after application to remove any surplus dye. If using a brush, apply 1 thin coat, followed by a second coat if there is still suction in the wood. Again, wipe off any surplus dye with a cloth. When the dye is thoroughly dry, the wood may be either wax polished, French Polished, or varnished, as desired. Teak oil, Tung oil, Danish oil, linseed oil, olive oil (for food contact woods)
French polish Very seldom used in schools. Basically the polish is rubbed into the smooth material and buffed into it providing it with a high shine. It is muscle building work to french polish an item. It is also very time consuming to apply. The subsequent surface is neither heat resistant or water resistant but it looks very good with an enhanced and shiny grain pattern. . Internal high quality furniture Varnish http: //www. blackfriar. co. uk/default. asp Varnishes can be used to provide a wooden artefact with a tough and durable surface and some resistance to heat, boiling water, knocks, dilute acids, alkalis and stains. It can also be used to give furniture new life and bring out the natural grains and colours of wooden surfaces. Varnishes are available for both internal and external use. APPLICATION Ensure surface to be varnished is clean, dry, sound and free from wax and oil. If preparing bare wood sand it to a smooth surface always working with the grain of the wood. If varnishing a previously coated surface sand lightly to provide a key. Where it is suspected wax may have been used, clean surface thoroughly with white spirit prior to sanding. apply varnish evenly, using light strokes, following the grain of the wood. Rub the varnished surface lightly with a slightly damp cloth and allow to dry. For best results 3 -4 coats are recommended. If more than 24 hours elapse between coats, lightly rub the surface down with fine glasspaper, working with the grain and then remove the dust. If you're applying by spray, thin the varnish with up to 10% white spirit and spray as normal. External wood- boats/yachts, furniture. Internal furniture Wax finishes This uses natural waxes such as beeswax, carnauba etc to seal and Internal furniture only enhance the wood, adding lustre and shine while controlling moisture. These waxes are not water or heat resistant. http: //www. tep. org. uk/a 2 z_glossary/a 2 z/finishes. htm Cellulose sealant (sanding sealant) A nitro-cellulose materials that dries very rapidly sealing the wood and raising the grain to enable a smoother finish to be achieved. The wood will then accept a wax finish. http: //www. tep. org. uk/a 2 z_glossary/a 2 z/finishes. htm Internal furniture only. Tannalizing (Treated Timber) This is timber which has been impregnated with wood preservative under controlled conditions. Pressure treated timber has a long service life and is protected against fungal and insect attack. Fence posts, decking, joists, battens, Suitable timbers for treatment are all softwoods, commonly used hardwoods and exterior grade plywoods.
BRAZING METALS What is Brazing Preparation of materials Involves melting a metallic filler material to form a permanent joint between two pieces of metal that are to be joined. The metals being joined are not melted in the process Clean the pieces to be joined and locate them accurately against one another. In school we use a torch. . Apply flux to the surfaces to prevent oxidation when the metals are heated. The flux lets the filler run smoothly between the two surfaces without forming a clump and hence a weak joint. Process Use the brazing torch to heat the metals to the right temperature depending on the metals being joined and apply the brazing rod between the metals where it melts and flows. As the brazing material cools it forms a strong permanent joint between the materials. Advantage over other processes Brazed joints are smooth and complete, creating an airtight and watertight bond. It also conducts electricity like the base alloys. Brazing can be used to join dissimilar metals such as bronze, steel, aluminium, wrought iron, and copper, with different melting points.
Part 2 lean and c ntil it is shiny d dry paper u an metal with wet • Clean fan on the extraction • Turn ot light to light the pil er he vice • Ask the teach r in the vice (T bricks o stop it her on the fire ur work eit azed earlier to been br • Set up yo work that has rt e used to suppo
• Heat up your metal where you want to join it until red hot • Quickly heat up the end of the brazing rod and dip it into the flux to coat the end • Heat up the metal till just red then introduce the rod tip and flux into the flame, melt enough brass to join the metal ( not too much as you will have to file away any excess later!)
This machine is used to cut slots and shapes out of metal. The milling cutter is held firmly in the head of the machine and then lowered into the metal whilst rotating. The bed of the machine (with your work held firmly in a vice) is then moved to cut slots etc. We have The CNC ( computer Numerically Controlled) Milling machine is used for cutting slots, grooves and shapes out of wood, metal and plastics. The computer programme is converted into X, Y, Z coordinates, the codes that say where the cutter is at any one time. Again the cutter stays still whilst the bed moves. CAD – Computer Aided Design CAM – Computer Aided Manufacture
Used for drilling the mortise part of the MORTISE and TENON joint.
In Industry you would have a set of files for each material area, unfortunately we cannot do that! The most common tool for shaping materials is the file. They come in various shapes as shown above. For very fine or intricate work choose needle files, these are delicate and can be quite expensive. We CROSS file to remove material quickly, this can leave a rough edge or BURR We DRAW FILE to give a better finish and remove scratches.
True 'sandpaper' (i. e. backing paper covered with grains of sand) is no longer available commercially but has been replaced by backing sheet covered with glass, aluminium oxide, silicon carbide, garnet or other specialist grit. Generally the terms 'sandpaper' and 'glasspaper' are used generically to cover all types of grit attached to a backing sheet. Once the major manufacturing process has been completed woods need to be finished with a protective and sometimes decorative finish. Before a finish can be applied work must be rubbed down to get rid of dirt, scratches and to create a smooth surface. A good finish can only be achieved with a good flat surface underneath Grit size Grade 40 -60 course 80 -100 Med course 120 -150 med 180 -220 fine 240 up Very fine Available in: Sheet Size – 280 x 230 Rolls, Discs, Belts Start with a rough grade of paper and work through to a fine grade. If you are working in metal rubbing down removes the grease that is stopping the moisture in the air from making your work rusty. It is important to apply your finish as soon as possible to avoid your work getting dirty again. When finishing wood with paints and varnishes the first coat will readily be absorbed by the wood, so you may need to rub your work down between coats using fine papers to achieve a smooth (Wet and Dry) Aluminium Oxide Paper finish. This is called CUTTING BACK Always rub along the grain Silicon Carbide Paper Flour Paper Garnet Glass paper Paper
Types of grit Glasspaper Generally composed of quartz granules on a paper backing, this is an inexpensive, relatively soft abrasive for sanding painted or natural timber, metal, and other materials. It wears relatively quickly and is best suited to provide a roughish finish before a really smooth surface is attempted. Normally only available with non-waterproof adhesives/backing paper. Aluminium Oxide This man-made material is suitable for shaping, sanding and polishing hard metal such as iron and steel, but also effective on timber. Aluminium oxide cuts much faster and lasts longer than glass or garnet. It is available on non-waterproof, cloth or waterproof backings. Cloth backing offers flexibility and is suitable for heavy-duty applications, such as rust removal and metal shaping. Silicon Carbide (wet and dry) Silicon carbide paper, also known as 'wet and dry' paper, is suitable for both dry and wet sanding. It is suitable for sanding hardwood and plywood, soft metal like brass and aluminium, and plastic; also used for smoothing glass edges and frosting glass surfaces. It is fast-cutting and almost as hard as diamond, but it is brittle so the coarser grades will wear fast if used on hard metal. When used with water, it gives a very fine sanding of paint or varnish between coats. The wet slurry which forms will need to be wiped away during and after smoothing. Garnet Paper This is a natural crushed rock and is an excellent abrasive for general wood sanding, either by hand or with a power tool - it is recognised by its distinctive bright green colour. It now seems to be being replaced by Aluminium Oxide grit. Steel Wool Although not a sandpaper, Steel Wool is used for fine 'sanding'. It is much used by the serious cabinetmaker as it has a much finer abrasive effect than grit materials on sandpaper. The fine steel strands cuts rather than abrades the surface, producing very fine finishes; as the wool is used, small pieces of it break off and mix in with the sanding dust. Steel Wool is graded starting at a very coarse 5 through to a series of noughts - 0000 being the finest. Although excellent on timber and metal. Steel wool can be used to 'sand' complicated shapes such as metal castings or wooden mouldings.
Often when turning you need to repeat a shape ( for example when turning a set of table legs) A drilling jig A mitre clamp for holding work being glued Mitre box a jig to hold wood whilst cutting 90/ 45° Bench hook used against edge of bench to support work whilst cutting. These chess templates are made from steel. If you need to make more than one of your design then you can use a jig, mould, or template. A template is any device that allows you to mark out accurately without measuring each time or go directly to cutting. Jigs are used to hold work whilst drilling, folding, shaping or cutting. Moulds are used to form materials around or pour materials into e. g. vacuum forming or a jelly mould! Dovetail jig for router
In the exams you will need to give full answers including sketches and notes. Being familiar with the names and uses of the following tools will help. To lathe Marking gauge Engineers Square G Cramp Bench hook Chisel Coping Saw Try Square Spade Bit Mortiser
Odd leg calipers Tenon saw Mortise drill Centre punch Disc sander CNC (computer numerically controlled) milling machine G cramp Sliding bevel Scribe Router
Hegner saw Hole saw Mallet Tap Pillar drill Split die Forstner bit
There are 2 main types of plastic: Thermoplastics and Thermosetting Plastics Thermoplastics are sensitive to heat. This allows them to soften when heated and to be bent into a variety of shapes and forms. They become stiff and solid again when cold. This process can be repeated many times. The molecules of thermoplastics are in lines or long chains with very few entanglements. When heat is applied the molecules move apart, which increases the distance between them, causing them to become untangled. This allows them to become soft when heated so that they can be bent into all sorts of shapes. When they are left to cool the chains of molecules cool, take their former position and the plastic becomes stiff and hard again. This process can be repeated many times. Thermosetting Plastics They may be heated the first time and shaped but they become permanently stiff and solid. They cannot be reshaped again. The molecules of thermosetting plastics are heavily cross-linked. They form a rigid molecular structure. Whereas in thermoplastics the molecules sit end to end, the molecules in thermoplastics sit end-to-end and side-by-side. Although they soften when heated the first time, which allows them to be shaped they become permanently stiff and solid and cannot be reshaped. Thermoplastics remain rigid and non-flexible even at high temperatures. Polyester resin and urea formaldehyde are examples of thermosetting plastics. Plastic Memory. Each time a plastic is reheated it will attempt to return to its original flat shape unless it has been over heated or damaged. This is called a PLASTIC
All plastics are synthetic and originally derive from crude oil. Through a process called fractional distillation plastics and their additives are made. Plastics have many different uses and have to have many different qualities, so manufacturers have to use additives to make the plastic suitable for the products. The qualities can be altered by using the following additives: • Plasticisers which make the plastic more bendy • Antistatic to cut down the static electricity that plastic can carry • Antioxidants to reduce the degradation that occurs when exposed to UV light or air Us th ed er fo mo r pla s • Flame retardants which make the plastic more resistant to heat r g fo s) lue • Fillers which make the plastic stronger ed (us • Pigments which change the colour and pattern of the plastic s
Thermoplastics are sensitive to heat. This allows them to soften when heated and to be bent into a variety of shapes and forms. They become stiff and solid again when cold. This process can be repeated many times. Recycle code Common Name Properties Uses Cost Ovenable film and food trays, drinks bottles including baby bottles and strapping. Stiffness, strength, toughness, resistance to chemicals and moisture. Easy to process and form Milk, water, juice, cosmetic, dish and laundry detergent bottles. Yogurt and margarine tubs. Cereal box liners, grocery, bin and retail bags. Rigid PVC (poly vinyl chloride 1 Clear, tough, good gas & moisture barrier. recycled flakes and pellets in demand for spinning fibre for carpets and textiles and geo-textiles. Good heat resistance Wide range of colours. Stiff, hard. Tough at room temperature. Can be used outdoors if suitably stabilised. Light weight. Very good acid and alkali resistance. Particularly good for fabricating Thermoplastic medium Pipes, guttering and fittings. Bottles and containers. Curtain rails. Roofing sheets. Shoe soles. Brush bristles Low density polyethelyne Ease of processing, strength, toughness, flexibility, barrier to moisture Dry cleaning, bread and frozen food bags, injection moulded aeroplanes; buckets and bottles. Polyethelene Terephthalate (PET, PETE) Nickname polyester! High density polyethylene 2 (HDPE) 3 4 (LDPE) low medium
Recycle code Properties Uses Polypropylene 5 Common Name Good chemical resistance, strong, has a high melting point ( good for hot fill liquids). Yogurt containers and margarine tubs & medicine bottles. Found in flexible & rigid packaging & large moulded parts for autos and other consumer products. (PP) Polystyrene 6 (high impact polystyrene) (Also called Comes in a wide range of Compact disc jackets, meat colours. Easily formed retains trays, egg cartons, aspirin shape. Good for vacuum bottles, cups plates and cutlery. forming. Good insulator Cost Low HIPS) Stiff, strong and tough. Cameras, kettles vacuum Acrylonitrile Scratch resistant. Comes in a cleaners and other household Butadienestyrene wide range of colours. products widely known as ABS Nylon Acrylic (Also called PMMA) Stiff, strong and self lubricating Bearings, mechanical components. Clothing Scratches easily, formed into shapes using many methods Baths, spectacle lenses medium
They may be heated the first time and shaped but they become permanently stiff and solid. They cannot be reshaped again. Common Properties name Uses Other notes Thick clear liquid – used for Canoes, paperweights coating or mixing with glass reinforced plastic (GRP) Irritant, wear barrier cream Liquid made into 2 part glues gluing Also used for surface coating/laminating Urea formaldehyde Usually white, tough, brittle Electronic fittings Also made into cascamite glue Phenol formaldehyde Dark, hard, brittle, resists heat Pan handles If over heated gives off toxic fumes Polyester resin Epoxy resin
Smart Materials A new generation of materials. Kevlar ultra strong textiles protective clothing ranging from industrial gloves to weapon proof vests. The material is designed to combine the unique properties of different materials such as carbon fibre and kevlar; both of which have exceptional tensile strength. Polymorph Plastics • The revolutionary plastic that melts in hot water and can be moulded by hand • Hardens as it cools - strong as nylon • 101 uses for DIY and model making such as prototype mechanical parts or armatures and frames for models • Becomes easily mouldable at just 62°C. It can be heated with hot water or a hair dryer and moulded by hand to create prototypes and solve manufacturing problems currently outside the capacity of other materials. • Uses for Polymorph include: Prototype mechanical parts, torches Joining components together Mouldings for handles & orthopaedic aids Vacuum
Smart Materials A new generation of materials. THERMOCHROMIC SHEET This is an example of a Thermocolour sheet (made from Thermochromic material). It changes colour with heat. Apart from being fun it has been used to make Festival T-shirts and children’s cups and bowls that warn when they get hot ! SMART WIRE SMART wire shrinks when you pass an electric current through it. Here is an example of it being used as a security device to lock a door. Great for use in robotics!
Nylon is a thermoplastic silky material, first used commercially in a nylon- bristled toothbrushes (1938), followed more famously by women's “nylons” stockings (1940). It is frequently referred to as polyamide (PA). Nylon was intended to be a synthetic replacement for silk. Nylon fibres are used in a great many applications, including fabrics, bridal veils, carpets, musical strings and rope. Nylon – is different! WHY? Because it. . . • was the first commercially successful polymer and the first synthetic fibre to be made entirely from coal, water and air. • It is self lubricating which makes solid nylon ideally suited for use for mechanical parts such as gears and bearings and other low- to medium-stress components previously cast in metal. • High resistance to: insects, fungi and animals moulds, mildew, rot many chemicals. • Melts instead of burning.
MARKING OUT, CUTTING AND FILING PLASTICS The most common plastics used in school are acrylic and high impact polystyrene. Acrylic sheet has a protective film or paper to avoid scratches which are difficult to get rid of. Keep the coating there as long as possible and use pencil to mark out. If it is removed then you could use a permanent pen. If you are going to drill then masking tape should be put over the area so that the markings can be clearly seen and to stop the drill bit from slipping over the surface. Acrylic sheet comes in various colours and thicknesses. It is worth remembering that it is brittle so care must be taken when cutting. As long as it is well supported acrylic can be cut with tenon saws, coping saws and hegner saws, It can even be planed if the plane is set low and the plastic doesn’t twist. If cutting with a machine saw masking tape should be put along the line to stop the heat of the blade from fusing the cut back together again. If drilling big holes then a pilot hole should be drilled first. Many plastics can be snapped down a straight line, first score the line to weaken it and then clamp it between two pieces of wood. Make sure you wear goggles! After cutting the edges can be very rough in contrast to the lovely shiny top and bottom. Metalwork files of any size can be used to clean up and small needle files can be used to file small details. Care must be taken if filing across your work it best to file along your work.
This process can be compared to squeezing toothpaste from a tube. It is a continuous process used to produce both solid and hollow products that have a constant cross-section. E. g. window frames, hose pipe, curtain track, garden trellis. Plastic granules from the hopper are fed along a heated cylinder by a rotating screw. An example of a die The tapered shape of the screw compacts the plastic as it becomes plasticized. This part of the process is similar to the heating and compacting stages in the injection moulding process. The difference being that the softened material is allowed to flow out through a die in a continuous stream rather than be pumped intermittently in measured amounts into a mould. This photo shows the full length of the cooling trough and the extrusion passing through it on its way to be cut to length. Extrusion rates typically vary between nine and sixty metres per minute.
Injection moulding is a highly automated production process for producing large quantities of identical items. Process Example mould Moulds The two part mould shown in the photo has been machined from high chromium steel (stainless). Moulds like this one cost several thousand pounds to manufacture. However this can be economical as many thousands of components can be produced from a single mould thus resulting in a low cost per item. Plastic powder or granules are fed from a hopper into a hollow steel barrel which usually contains a rotating screw. The barrel is surrounded by a jacket of heaters which melt the plastic material as it is carried along the barrel by the screw towards the mould. The screw is forced back as the melted plastic collects at the end of the barrel. Once a sufficient charge of melted plastic has accumulated a hydraulic ram forces the screw forward injecting thermoplastic through a sprue into the mould cavity. Pressure is kept on the mould until the plastic has cooled sufficiently for the mould to be opened and the component ejected. Material Normally thermoplastics are used in this process although a few thermosetting plastics can also be injection moulded. Material properties of thermoplastic can be altered by adding plasticisers and other chemicals to improve such things as impact and ultra violet (UV) resistance. A wide range of colours are available and this is achieved by adding a 1% colour mix to the usually colourless raw material prior to melting.
Extrusion blow moulding is an automated process that is used extensively to make bottles and other lightweight , hollow parts from thermoplastic materials. Process The cycle starts with the mould open. A hollow length of plastic, called a parison, is extruded down between the two halves of the mould. (photo below) A tube of plastic is extruded The mould closes and compressed air is blown into the inside of the parison which inflates it, pushing the soft plastic hard against the cold surfaces of the mould. The plastic is cooled by the mould, causing it to harden quickly. The mould is then opened (below), the moulding ejected and the waste (called flash) is trimmed off with a knife. Moulds The mould is closed Moulds used for blow moulding tend to be less expensive than those used for injection moulding. Firstly, moulds used in blow moulding are less complicated than those used for injection moulding. They tend to be made in two parts with fairly simple, symmetrical, round shapes which can be machined easily. Secondly, because of the lower pressures the moulds can be made from aluminium instead of high carbon steel This also reduces the cost as aluminium is easier and quicker to machine than steel. Materials High density polyethylene (HDPE) and low density polyethylene (LDPE) are both commonly used for blow moulding as are other types of thermoplastics. The thermoplastic used in blow moulding needs to be more viscous (flow less easily) than that used for injection moulding as the parison must retain its form before the mould closes around it Air is blown in Mould opens and moulding removed Blow moulded garden gnomes and baby bottles
Thermoplastic sheet is heated This process is used to manufacture a variety of products in thermoplastic materials. These products range in size from garden pond liners to food trays used in supermarkets. A typical industrial size vacuum forming machine like the one seen below is capable of producing vacuum formings up to 1. 8 m x 1. 5 m in size. Process Heater removed and air blown in The platen is raised A mould is attached to a platen (support plate). The platen and mould are then lowered and rigid thermoplastic sheet material is clamped onto an air tight gasket and usually heated from above. Once thermoplastic sheet is softened enough (i. e. reaches a plastic state) then air is blown in to raise the sheet in a slight bubble before the platen is raised bringing the mould into contact with the plastic. Any trapped air remaining between the platen and the heated plastic sheet is then evacuated by a vacuum pump. Atmospheric pressure acting over the top surface completes the forming process by pressing the plastic sheet onto the mould. Once the plastic sheet has cooled down to below it's freeze point the air flow is reversed to lift the forming off the mould. If this is not done quickly the forming tends to grip onto the mould and attempts to prise them apart often result in damage to the forming. Moulds A vacuum pump removes air Moulds can be made from a variety of materials such as wood, medium density fibreboard (MDF), plaster of paris and clay. MDF is probably the most suitable for "one-off" vacuum formings or short production runs in school workshops Having no grain it is relatively quick and easy to shape compared with solid wood and is also stable whilst being heated in the vacuum forming machine. For higher volumes of production it is necessary to manufacture moulds from harder wearing materials such as aluminium or cast epoxy resin. Materials Many types of thermoplastics are suitable for vacuum forming. The most popular is Polystyrene (HIPS). It is relatively cheap, comes in a wide range of colours and is easy to form. Typical thicknesses of sheet material used range from less than 1 mm up to 6 mm. Some thermoplastics (e. g. ABS) require pre-drying in an oven before vacuum forming as moisture blisters may appear on the surface when the material is heated if this is not carried out. The platen is lowered and the mould removed
This is, historically, the oldest commercial plastics moulding process and is mainly used to make products from thermosetting materials. A combination of heat and pressure is used to change the material's form and chemical structure. Plastic powder preform is placed in mould Press is lowered closing the mould Materials Typical thermosetting plastics used in compression moulding are urea formaldehyde and phenol formaldehyde. These materials are different from thermoplastics as they cannot be reheated and reshaped because a chemical change, called polymerisation, has taken place. Generally thermosets tend to be harder, stiffer and more resistant to the effects of heat and chemical attack than are thermoplastic materials. Polymer cross linking occurs The moulds are made in two parts from high chromium steel (stainless). Mould is opened and former released Compression moulded pan handle, make up containers, mobile phone cases and socket
Plastic film, sheet and coated materials such as wall paper and fabrics are produced by the calendering process. It involves rolling out a mass of premixed plastics material between large rollers to form a continuous and accurately sized film. The main material used is PVC, others include ABS and cellulose acetate. PVC ranges from flexible to rigid and the final product is composed of a number of basic materials which must be combined in a uniform mixture of measured ingredients. These ingredients include a resin of a specified molecular weight, stabilisers, lubricants, reinforcing materials, colorants and plasticisers. The process begins with the ingredients being blended and fluxed in a mixing mill (below) at approx. 100°C.
Line or strip bending is used to form straight, small curvature bends in thermoplastic sheet material. The process is quite straight forward. An electric element similar to that in an electric fire, is enclosed in a channel which has an opening at the top.
Rotational moulding is a process used mainly to manufacture hollow shaped products such as footballs, road cones and storage tanks up to 3 m³ capacity. Station 1 - the granules or powder are put into the 2 part mould As the mould rotates its inner surface passes continually through the mass of powder at the bottom of the mould. The powder in contact with the hot metal fuses and sticks to the mould surface. As the mould rotates (in all directions) more plastic melts and sticks to the inner surface finally producing an even layer up to 10 mm thick. The hollow moulding can be removed (Station 1) as soon as it is cool enough to hold its shape. . The only time the moulds are not being rotated is when they are positioned at Station 1 which is where the process both begins and ends. Here the moulds are either being loaded with thermoplastic powder or the finished mouldings are being removed. Still rotating (below), the mould moves into a cooling area or chamber (Station 3) where it is cooled by air or water jets.
Application of thermoplastic coating powders Plastic coating is the process of applying a thermoplastic to the surface of metal items to provide long-term corrosion, impact and chemical resistance whilst offering an attractive decorative finish. Plastics tend to be applied a little thicker than standard paints and are generally impermeable to water or aggressive chemicals. As a result thermoplastics are ideal for very long term protection of metal in the construction and automotive industries or for the coating of welded items such as wire baskets, fencing mesh and cylinders. The materials are supplied in powder (or liquid) form and are usually applied in the factory by standard fluid-bed (fluidised bed) or electrostatic spray techniques. All Plascoat products for the appliance industry offer: An attractive finish providing long-term protection Ease of coating - often with reduced energy usage Comprehensive coverage - including for sharp metal edges and welds Freedom from the traditional problems of cracking and peeling Food and water contact approvals
same time! A Bit of light relief… and learning at the Plastics and Recycling
Plastics that break down Biochemical researchers and engineers have long been seeking to develop biodegradable plastics that are made from renewable resources, such as plants. The term biodegradable means that a substance is able to be broken down into simpler substances by the activities of living organisms, and therefore is unlikely to persist in the environment. There are many different standards used to measure biodegradability, with each country having its own. The requirements range from 90 per cent to 60 per cent decomposition of the product within 60 to 180 days of being placed in a standard composting environment. The reason traditional plastics are not biodegradable is because their long polymer molecules are too large and too tightly bonded together to be broken apart and assimilated by decomposer organisms. However, plastics based on natural plant polymers derived from wheat or corn starch have molecules that are readily attacked and broken down by microbes. Biodegradable plastics made with plant-based materials have been available for many years. Because of their higher cost they have never replaced traditional non-degradable plastics in the mass market. Indeed, biodegradable plastic products currently on the market are from 2 to 10 times more expensive than traditional plastics. But environmentalists argue that the cheaper price of traditional plastics does not reflect their true cost when their full impact is considered. For example, when we buy a plastic bag we don't pay for its collection and waste disposal after we use it. If we add up these associated costs, traditional plastics would cost more and biodegradable plastics might be more competitive.
The energy for a system may come from many different sources such as wind or water. This energy then has to be converted into the most appropriate form to perform a task; this can be complex as it often combines different mechanisms. Click here to see some more truly entertaining mechanical toys http: //www. cabaret. co. uk/
LINEAR MOTION Linear motion is the most basic of all motions. Linear motion takes place in a straight line like a sliding door, if you constantly opened and closed the door then it would be reciprocating motion. Linear motion is measured in two parts. Speed, and direction. Together these make up the velocity. RECIPROCATING MOTION Reciprocating motion is back and forth motion. Reciprocating motion is measured by its throw (the distance between the two extremes of motion) and by its period (the length of time for each cycle) An example is a swinging backwards and forwards. Rotary Motion Rotary motion is when something spins in a circle, like a bicycle wheel. Measurement: Rotary motion is measured in either angular velocity, the number of degrees turned in a given time, or in revolutions per minute (rpm). OSCILLATING MOTION Oscillation is back and forth motion about a pivot point. It is measured in terms of both the angle of throw (amplitude) and the period of time for one complete cycle (periodic time) or the number of cycles in a given time (frequency). Click here to see more mechanisms @ http: //www. technologystudent. com/cams/camdex. htm
CAMS An eccentric cam is a disc with its centre of rotation positioned ‘off centre’. This means as the cam rotates the flat follower rises and falls at a constant rate. This type of cam is the easiest to make and yet it is one of the most useful. Irregular motion is motion which has no obvious pattern to its movement. It is often needed in automata to recreate the movements of living things. Irregular motion is usually created using a cam or series of cams Irregular motion is not often used as the starting point for a mechanism. To stop it from jamming the example must turn anti-clockwize! Also, to ensure the rotation is smooth, the vertical centre line of the snail/drop cam is positioned slightly to the left of the slide Eccentric, heart shaped and pair shaped cams generally allow for a slow rise and fall of the follower.
Spur Gears Spur gears are the most common type of gears. They have straight teeth, and are mounted on parallel shafts. Sometimes, many spur gears are used at once to create very large gear reductions. Spur gears are used in many devices On any gear, the ratio is determined by the distances from the center of the gear to the point of contact. For instance, in a device with two gears, if one gear is twice the diameter of the other, the ratio would be 2: 1. Helical Gears The teeth on helical gears are cut at an angle to the face of the gear. When two teeth on a helical gear system engage, the contact starts at one end of the tooth and gradually spreads as the gears rotate, until the two teeth are in full engagement. This gradual engagement makes helical gears operate much more smoothly and quietly than spur gears. For this reason, helical gears are used in almost all car transmissions. Spur gears can be really loud. Each time a gear tooth engages a tooth on the other gear, the teeth collide, and this impact makes a noise. Bevel gears can be used to change the direction of drive in a gear system by 90 degrees.
This is a good example of a ‘gear train’. A gear train is usually made up of two or more gears. The driver in this example is gear ‘A’. If a motor turns gear ‘A’ in an anticlockwise direction; Which direction does gear ‘B’ turn ? Which direction does gear ‘C’’ turn ? An ‘idler’ gear is another important gear. In the example opposite gear ‘A’ turns in an anticlockwise direction and also gear ‘C’ turns in an anticlockwise direction. The ‘idler’ gear is used so that the rotation of the two important gears is the same. Is the speed of gears A and B the same ? It would be very difficult to draw gears if you had to draw all the teeth every time you wanted to design a gear system. For this reason a gear can be represented by drawing two circles. CIRCLES OVERLAP WHERE TEETH MESH
RACK AND PINION Linear Rotary As the handle is turned the table moves up and down the central pillar of the drill. This makes it easy to move the table and takes the minimum of effort. The rack and pinion reduces the force needed to move the table and most importantly protects the machine operator and his/her back from excessive strain.
Worm gears The arrangement of gears seen left is called a worm and worm wheel. The worm, which in this example is brown in colour, only has one tooth but it is like a screw thread. The worm wheel, coloured yellow, is like a normal gear wheel or spur gear. The worm always drives the worm wheel round, it is never the opposite way round as the system tends to lock and jam. The picture to the right is a typical set-up for a motor and worm gear system. As the worm revolves the worm wheel (spur gear) also revolves but the rotary motion is transmitted through a ninety degree angle.
PULLEY SYSTEMS Pulley systems are used when there is a need to transmit rotary motion. The diagram shows a simple system comprised of two pulley wheels and a belt. It is a simple mechanical device to winch up and down a rope. When the motor is turned on it revolves the driver pulley wheel. The belt causes the driven pulley wheel to rotate as well, winding out the rope. Pulley wheels are grooved so that the belt cannot slip off. Also, the belt is pulled tight between the two pulley wheels (in tension). The friction caused by this means that when the driver rotates the driven follows. • Most pulley wheels have a central shaft on which they rotate. To keep the wheel firmly attached to the shaft it is usual to use what is called a ‘key’. The diagrams to the left shows a keyed shaft which is pushed through the centre of the pulley wheel. A small rectangular key is then ‘tapped’ into position, holding the shaft and the pulley wheel together. This fitting means that the pulley wheel cannot slip on the shaft.
PULLEYS Pulleys have several advantages over gears but also some disadvantages. The main advantage is the fact that they are simple to make and can be used at a distance from each other unlike gears that need to touch in order to work. The disadvantage is that they work by friction and so can slip. You can get a toothed pulley and belt which eliminates any slipping or timing problems. Many cars have a cam belt that works on this principle. The belt can be substituted for a chain. A bicycle is a good example of this principle. You may have noticed that pulleys rotate in the same direction Rotary Rotary
Pulleys are useful for getting the drive action to happen in awkward places. You can use the drive pulley to transmit its motion to the output pulley which may be some distance away. We can also use pulleys to reverse the action by putting a twist into the belt. This makes the output pulley move in the opposite direction. Again this can be very useful at times. When you want to transmit the drive over some distance, then pulleys are an ideal choice they are simple to construct and take up comparatively little space. They produce a constant and smooth drive force. You can change the direction of drive. This can be to any angle but the most common use would be to turn the drive through 90 degrees. This same task could be performed by gears but would be significantly more difficult to make. You can use the pulley to either step up or step down the drive simply make the diameter of the pulley wheels larger or smaller. The ratio 2: 1 means for every 2 revolutions of the input pulley the output turns one full revolution. You could of course reverse this around. http: //www. flying-pig. co. uk/mechanisms/pages/pulley. html
Cranks are similar to a simple cam. They convert circular movement into a reciprocal one (up and down motion) or vice verse. How ever there are some fundamental differences. Firstly cranks only ever work in a circular motion and they only have one drive action per revolution. CRANKS Although the crank only works in a circular motion, its drive can be made to go from side to side as well as up and down. Another big advantage with the crank is having power on both the upward and return strokes. This means you don’t have to rely on gravity which can be a problem with cams. Rotary Reciprocal and Oscillating
RATCHET ALTERNATIVE GEARS The ratchet is really another form of gearing. Unlike gears which can be used to speed up or slow down movement, the ratchet can only be used to slow things down and it happens in a very jerky manner. Below is an explanation of how they work. For every 8 turns of the crank the ratchet wheel turns one complete revolution. This gives a ratio of 8: 1. The pawl is rotated on a crank and pushes the ratchet wheel one notch for every revolution. It will take 8 turns of the crank to produce one complete turn of the ratchet wheel. TAKING ADVANTAGE The ratchets disadvantage of a jerky movement can be taken advantage off. The automata uses this movement to build up suspense before finalising in a big finish The crank turns clockwise which helps to push the pawl or catch down onto the ratchet wheel
Linkages are an essential part of many mechanisms. They can be used to change direction, alter speed and change the timing of moving parts. In this example two linked linkages are used to convert the small linear movement of the drive shaft (bottom left) into first a rotational body movement and secondly a fast hammer movement. Compare the speed of the hammer with the speed of the drive shaft! This time, two different lengths of bar, the two long bars, yellow and red are the same length as before. Look at the tip of the red shaft, notice how it moves smoothly until the last second then flips to the right. The same effect is used in the Motley Man to make him look up at the last moment of his bow. www. flying-pig. com/mechanisms/pages/linkage. html The basic 4 bar linkage. All four bars make up a parallelogram. Two, equal length orange shafts and the distance between the joints on the red moving bar and yellow fixed bar being equal. The movement of the top arrange shaft exactly shadows the movement of the lower orange bar. By changing these lengths and the lengths of the other bars different movements can be achieved. Quite an extreme arrangement this! With the two long bars crossing over each other. A more extreme 'kick' in the orange bar this time at the end of the green bar's travel. Looks like a likely mechanism for a model!
There are 4 types of construction in wood: Carcase or box construction is where planks or flat pieces are joined together to make box shapes such as shelves, wardrobes, boxes, drawers Stool frame is where a supporting frame is made from legs or rails such as tables, stools and chairs Flat frame is where pieces are joined together to make such things as doors, windows and picture frames Slab construction is where sheets of wood, usually man-made, are joined using simple permanent or knock down fittings
Butt joint very easy to construct Lap or rebate joint easy to but very weak. Can be strengthened by nailing construct and of average strength Housing joint An easy joint to Mitre joint Difficult to get angle accurate, can be strengthened with pins or dowels. Weak joint construct if marked out accurately. Of average strength. Can be made as a stopped housing where the joint does not come right to the front. Dowel joint with a jig to help line up the holes this is a very easy and reasonably strong joint to construct
A groove joint is a simple and fairly strong way of attaching a drawer bottom. By leaving the groove open at the back of the drawer it is easy slide in the drawer bottom after the rest of the drawer has been assembled. Nowadays grooves are usually cut with a power router. Finger joint a very effective looking joint that is hard to construct as it needs to be accurately marked out and cut to look good. A rebate joint allows a panel to be easily inserted into a door or cabinet back after the frame or carcase has been assembled. Panels can be pinned or held in place using lengths of moulding.
Corner mortise and tenon joints are used on tables and front legs of chairs where two rails are joined to a single leg at each corner. The ends of the tenons are mitred where they meet inside the leg. Haunched mortise and tenons are often used when joining corners of frames, or rails to the ends of legs. The tenon is offset to prevent it breaking through the end grain of the leg or stile. The haunch, which forms a small integral tongue on the tenon, supports the top edge of the rail. Dowel joints have replaced many traditional joints in factory made furniture. E. g. when joining rails or feet to round legs it is easier use dowel joints than mortise and tenons. The ends of the rails or feet can be shaped to fit the curve of the legs before drilling holes for the dowels to be inserted. Dowelling jigs are often used to ensure accuracy. The Dowels themselves are often made from a hard wood called Ramin, come in a range of diameters from 4 - 25 mm and typically have a grooved surface to allow the glue to flow easily along the dowel when it is inserted into the hole. Corner Bridle joints can be used on frame constructions which will not be subjected to high sideways pressure as this can force the joint out of square. To increase strength, dowels are often inserted through the side of the joint after gluing.
Through mortise and tenons are often used on doors and gates. This joint has the tenon passing right through the leg or stile. Twin mortise and tenons are used when joining thick rails to wide legs or stiles. A twin tenon is stronger than a single tenon on thick rails because of the increased gluing area. Each tenon should be as thick as the gap between them. A twin mortise and tenon is also used when a rail, turned on its side is joined into the face of a leg. Wooden wedges are often used to lock the tenon in place in situations where the joint has to withstand more than normal amounts of leverage.
Dowel joint Butt joint Solid timber is often too narrow for cabinet work and therefore must be joined along its edges to produce the desired width. Edge-to-edge butt joints are the simplest to make and, with modern glues, are normally strong enough for most situations. These joints can be reinforced by inserting biscuits, dowels, splines or tongues between the edges being joined. This type of joint is most suited for production using machine tools. To ensure large areas such as tabletops stay flat it is normal to 'match' the boards prior to gluing. This means reversing the direction of the end grain on each alternate board so that any movement that may occur later across the boards will be evened out. Biscuit joint Tongue and groove
Frames of panelled doors are often grooved on the inside to accommodate the panel. If haunched mortise and tenon joints are used at the frame corners it is usual to align the grooves with the mortises and make them both the same width. Depth of groove should be the same as the length of the haunch.
Twist Drill Used for drilling holes in wood, metal and plastics. The most used type of drill, made from carbon or high speed steel. A normal drill set will include sizes from 1 mm to 14 mm. For wood the largest hole should be 8 mm otherwise it leaves a ragged hole! Hole Saw For large diameters a 'hole saw' can be used. The advantage of this type of drill bit is that the blade can be changed to give different sizes of diameter. Forstner Bit Used for larger diameter holes. When using this bit the hole is drilled very slowly so that the bit does not 'jam' in the wood. You can use the forstner bit to drill part way through material. Spade bit/ flat bit These are used in electric drills for fast accurate drilling in both hard and soft materials. Used at the highest speed available. Locate the point before starting and make sure that drill has stopped before removing bit. Sizes available 6 mm to 40 mm Counter sink These are used for countersinking holes in wood, metal and plastic for screw heads and rivets.
Screws are used to fit materials such as chipboard, MDF and natural woods together although there is a type of screw called a self-tapping screw that can be used for joining thin metal sheet. Drilling accurately sized holes in preparation for your screws ensures that the materials to be joined will be pulled tightly together. If gued at the same time this is a very effective and permanent way of joining wood. Types of hole A pilot hole must be smaller - slightly smaller than the core of the screw - so that the core fits tightly into it. A clearance hole must be very slightly bigger than the shank of the screw, so that the shank can move freely in the clearance holes. A counter sunk hole allows the top of the screw head to be flush with the surface. DOME HEAD SCREW: Can be used for fitting fixtures such as mirrors. The 'cap', which is the dome shape is usually chromed or made from brass and this can be a good feature. It also makes the head of the screw safe as the doom has no sharp edges to catch and cut hands/fingers. CHIPBOARD SCREWS: The thread on this type of screw extends all the way along the length. It is best used with chipboard SELF-TAPPING SCREWS: these are normally used to cut a thread in metal. A hole is drilled in the metal, a fraction smaller than the width of the screw. The self-tapping screw is then turned into the hole cutting a thread. Round headed wood screw: Used to fit door handle plates and decorative features that must look good.
Using nails is an effective way of fixing or joining pieces of softwood together. Hardwoods can be difficult to join with nails as they tend to bend under the impact of the hammer. Below is a range of nails that can be used depending on the type of wood and the nature of the work to be attempted. ROUND WIRE NAIL - This is used for general work. It is not attractive in shape and it can split wood when hammered in position OVAL WIRE NAIL - This is a long nail and care must be taken when it is hammered into the wood. It is unlikely to split the wood. LOST HEAD NAIL - This is ideal if it is necessary to hide the head of the nail as a punch can be used to hammer the head beneath the surface level. PANEL PIN - A very popular way of joining woods although glue is usually included as part of the join. TACK - Can be used for fixing textile materials to wood for example, fixing upholstery to furniture. SPRIG - This no head and is generally used for fixing glass to glass in wood frames. ANNULAR NAIL - The teeth of this nail hold it in place firmly. Therefore, it is used for fixing plywood and other materials. HARDBOARD PIN - The diamond shaped head is hidden when used in materials like hardboard CORRUGATED FASTENER - This will hold the corners of wood frames firmly together
Rivets are mainly used for joining Sheet Metal Riveting • A rivet is a metal peg with a head on one end • Rivets are used for mainly joining pieces of metal • A hole is drilled through both pieces and the rivet inserted with a set (hammer like tool). The head is held against the metal whilst the other end is flattened and shaped into another head with a hammer. • Pop (or Blind rivets) are now very common. They can be used where there is only one access to one side of the material ( hence blind rivet). A fast and easy way to join sheet metal. Dome Head Rivet The low-profile dome head is appropriate for most applications. Large Flange Rivet However, when soft or brittle materials are fastened to a rigid backing member, the large flange head should be considered, because it offers twice the bearing. surface. Countersunk Rivet Where a flush surface is required, the countersunk head style should be selected. With its neat appearance and low profile, this is the most versatile and most commonly specified head style. The dome head has twice the diameter of the rivet body, providing enough bearing surface to retain all but extremely soft or brittle materials. Available in a very wide range of materials. Large Flange POP brand rivets have twice the under-head bearing surfaces of comparable dome head rivets and are designed for applications where soft or brittle materials must be assembled to a rigid backing material. This head design is specified wherever a flush surface is required. Available in a variety of sizes and materials.
Plain Rivets Pop Riveting is an ideal method of joining 2 metal sheets materials together without distorting them through the use of hot joining methods. Riveted joints can be quite attractive if done accurately and carefully. 1. Drill to size Close the plates together Rivet is pushed into hole Hammer the head of the rivet to shape Rivet is squeezed using a rivet tool Finish the shape of the rivet using a rivet set The head snaps off leaving a riveted joint
BUTT HINGE Comes in a range of sizes from 13 mm to 150 mm and is normally used for room and cupboard doors, small boxes and windows. They fit neatly onto the edge of the wood so that they are barely visible when the door is closed. They are very strong but cannot be adjusted once they are fitted. BUTTERFLY HINGE This is often used on light-weight doors. Different shapes and patterns are available. They are generally easy to fit. Often made from brass CONTINUOUS or PIANO HINGE This is a hinge that comes in different lengths and can be bought in brass or steel. It is ideal where a long hinge is required such as a desk top or a cupboard door. Small countersink screws are normally used to fix it in position. FLUSH HINGES Lightweight hinge where one part fits into the other when closed. Often made from thin plated steel. Hinges come in a vast range of shapes and sizes, each designed to do a specific job. Before fitting your hinge you need to make a pilot hole and make sure that you have a good depth of material below the hinge. The hinge must be fitted accurately if it is to work properly!
CONCEALED HINGE These normally come in two sizes (25 mm and 36 mm. The hinge is adjustable once fitted and is designed with chipboard and MDF in mind. Commonly used in kitchen cupboards. BARREL HINGE This comes in two parts. The threaded part of the hinge is screwed into a pre-drilled hole. They are easy to fit and the hinge can be dismantled. TEE HINGES are used on shed doors and gates. The long arm spreads the load across several planks of the door whilst the short one fits onto the frame. Magnetic catch Draw bolt Nylon spring clip catch Ball catch
KNOCK DOWN FITTINGS Knock down fittings or KD fittings are used primarily with cheaper furniture made from manufactured boards. Items are often bought flat packed and can be easily assembled with minimum skill. PLASTIC CORNER BLOCK (FIXIT BLOCKS): The corner block is pressed against the two pieces of material (normally wood based). Screws are used to fix the block into position. This type of joint is used to fit modern cabinets such as those found in a kitchen. It is a relatively strong joint although it has the advantage that it can be dismantled using a screwdriver. NATURAL WOOD FITTING (SQUARE SECTION BATTEN): A piece of material such as pine can be drilled and screws can be passed through these holes. This gives a cheap and effective knock-down joint. The screws are normally countersunk into the knock-down fitting. TWO BLOCK FITTING (LOK-JOINTS): These are made from plastic. A bolt passes through the first fitting into the thread of the second. As the bolt is tightened it draws the two fittings together. The pins help keep the fitting straight. This gives a very strong joint and it can be dismantled using a screwdriver. RIGID JOINT: These are normally moulded in plastic which makes them strong. Screws pass through the four holes which hold the sides at each corner firmly together.
KNOCK DOWN FITTINGS SCAN FITTINGS: These are strong enough to be either permanent or temporary joints. The cylinder is inserted into the first side of a cabinet in a pre-drilled hole. The screw is then pushed through the hole in the second side until it meets the cylinder. It can then be tightened with a screw driver until both sides of the cabinet pull together. CAM LOCKS: The disk fits into a recess in the first side of the cabinet. It rotates by inserting a screwdriver into the slot in its side. The shaft is screwed into the second side of the cabinet. The collar of the shaft is passed through the hole in the second slot in the disk. When the disk rotates the shaft is locked in position. This keeps both sides of the cabinet locked together. Knock-down fittings can be put together easily, normally using only a screw driver, a drill, a mallet/hammer and other basic tools. Although they are temporary joints many can be used to permanently join items together Corner plates Barrel nut and bolt